Cooling system

ABSTRACT

A system for simultaneously proving coolant at one temperature to the cylinder jackets of a diesel engine and coolant at a low temperature to the engine air-charge intercooler, with the use of a single pump, heat exchanger, and temperature control valve. Only that portion of the coolant going to the intercooler passes through the heat exchanger, with the discharge thereof mixing with the engine coolant discharge to bring its temperature down to the desired engine coolant temperature. The temperature control valve controls the amount of coolant going through the heat exchanger so that the engine coolant remains at substantially the desired temperature.

United States Patent 11 1 1111 3,863,612

Wiener 1 Feb. 4, 1975 [54] COOLING SYSTEM 3,442,258 5/1969 -Ruger 60/13Inventor: Leonard Stem Wiener, Erie Pa. 3,483,854 12/1969 Foran 60/13[73] Assignee: General Electric Company, Erie, Pa. primary Examine,Manue| A Amonakas [22] Filed; Sept 7 7 Assistant Examiner-Daniel J.OConnor Attorney, Agent, or Firm-Walter C. Bernkopf; Dana [21] Appl.No.: 398,251 p gigelow [52] U.S. C1 123/4108, 60/13, 123/4109, B R T123/41.29,165/35, 165/36 [57] A ST AC [51] Int. Cl. F01p 7/14 A y m f rsimultaneously proving coolant at one [58] Field of Search 123/4109,41.08, 41.31, mper re to he cylinder jackets of a diesel engine123/4105, 41,29; 60/13; 165/35, 36 and coolant at a low temperature tothe engine airv charge intercooler, with the use ofa single pump, heat[56] Referenc s Cit d exchanger, and temperature control valve. Onlythat UNITED STATES PATENTS portion of the coolant going to theintercooler passes l 346 331 M920 M 123/4 09 through the heat exchanger,with the discharge l806l53 5/1931 l23/4l'05 thereof mixing with theengine coolant discharge to l890745 12/1932 'i'f" 123mm bring itstemperature down to the desired engine cool- 2:517: 2 3/1950 w 123/4109ant temperature. The temperature control valve con- 2,622,572 12/1952Nallinger 123/4109 trols the amount of Coolant going through the heat2,654,354 10/1953 Sanders 123/4105 changer so that the engine coolant.remains at substan- 3,229,456 1/1966 Gratzmuller 60/13 tially thedesired temperature. 3,397,684 8/1968 Scherenberg 60/13 3,425,400 2/1969Scherenberg 60/13 8 Claims, 2 Drawing Figures 1 29 I r /a /3 /4EXPANSION TANK ENGINE INTERCOOLER 5 .7 l7

l6 V Z1 l5 2/ COMPRESSOR estate EXCHANGER MEDIUM ,24 M

VPATENTEDFEB 4:915

M29 /8 l3 4 EXPANSION I TANK T ENGINE INTERCOOLER 5 I7 27 I0 I5 2/COMPRESSOR 22 E 23 c B HEAT EXTERNAL EXCHANGER COOLING MEDIUM 24 M HF/G. 2

/a' /3 EXPANSION TANK ENGINE INTERCOOLER l6 /9 COMPRESSOR 33 25 EXTERNALHEAT EXCHANGER i COOLING SYSTEM BACKGROUND OF THE INVENTION Thisinvention relates generally to cooling systems and more particularly tosystems for cooling internal combustion engines having elements withdifferent temperature requirements.

It is known in the art to control the temperature in a cooling system bythe use of a temperature sensitive valve to regulate the coolant flow ina system having a heat exchanger and circulating pump. Selectiveplacement of the valve determines the point in the system where aconstant temperature is to be maintained. Such a system isconventionally used in automotive applications wherein a three-waythermostatic valve regulates the engine water temperature by modulatingthe flow of coolant discharge passing through either a radiator or aby-pass line to the pump. This system is used for maintaining adesirable coolant temperature and flow relationship to effectively coola single heat element.

In some instances, it is desirable to cool more than one element in asystem, with the heated elements having different coolant temperaturerequirements. For example, in a diesel engine apparatus, where the aircharge is compressed by a turbocharger, it is desirable to cool thecompressed air as well as the engine itself. However, to maintainturbine inlet temperature within a tolerable limit, it may be necessaryto maintain the coolant into the intercooler which cools the engine airat a considerably lower level than that of the coolant for the cylinderjackets. Ordinarily, this requires two separate cooling systems completewith pumps, heat exchangers and temperature control valves, therebyamounting to considerable expense in installation and maintenance.

It is therefore an object of this invention to provide a cooling systemfor cooling plural heat sources having substantially differenttemperature requirements.

Another object of this invention is the provision in a cooling systemfor diverse coolant temperatures with a singular thermostatic valve andheat exchanger.

Yet another object of this invention is the provision in a coolingsystem for maintaining a substantially constant coolant temperature intoone element of the system while providing coolant at a considerablylower temperature to another element in the system.

Still another object of this invention is the provision for an enginecooling system which is economical to manufacture and operate.

These objects and other features and advantages become more readilyapparent upon reference'to the following description when taken inconjunction with the appended drawings.

SUMMARY OF THE INVENTION Briefly, in accordance with one aspect of theinvention, a closed cycle cooling system simultaneously provides liquidcoolant at different temperatures to each of two connected machines ormachine elements to be cooled using a single pump, temperature controlvalve and external heat exchanger. The flow of coolant to each of thecooled machines is in a constant preset proportion with the temperatureof the flow to one being regulated while the temperature to the otherdecreases as the load is increased. All the external cooling is done onthe coolant that flows through the machine or element requiring thelower temperature. After passing through and cooling that machine, itstemperature is still lower than that of the coolant leaving the othermachine. Mixing of the two coolant streams results in coolant at theregulated temperature being supplied to the regulated temperaturemachine and to the temperature control valve.

The underlying principle is that of removing the entire heat load fromonly a fraction of the coolant flow, thereby reducing its temperaturesubstantially below that which result by taking the same amount of heatout of the total coolant flow. The same principle may be applied in anunregulated temperature system, without a temperature control valve, toprovide colder coolant to one of two cooled elements.

The closed coolant circuit consists of a pump, a first machine elementrequiring cooling, a second machine element requiring cooling to a lowertemperature, a heat exchanger, and interconnecting piping or passages.

The flow out of the pump divides in two branches,

one going to the first machine to be cooled, the other going to the heatexchanger, thence to the machine to be cooled to a lower temperature.Leaving the cooled machines, the flow branches join and the coolantreturns to the pump inlet for recirculation.

For a regulated temperature system, a temperature sensor and atemperature control valve are provided and may be located either in theclosed coolant circuit or external to it, depending on the: particulareffect and arrangement desired.

When used in a diesel engine cooling system, a proportionate amount oftotal coolant flow is passed through the engine at a desiredtemperature. The other portion is directed to a temperature sensitivevalve which modulates, in response to the coolant temperature, thecoolant flow to the intercooler between two flow paths, one through aheat exchanger and the other through a by-pass. The heat exchanger thenreceives only a small portion of the entire coolant flow and cools it toa greater degree than is done in a conventional system. The coolantdischarge from the heat exchanger passes to the intercooler along withthe by-pass flow, and the resultant mixture is formed at a considerably,lower temperature than the coolant to the engine,

thereby allowing for increased cooling of the compressed air and greaterpower output in engine operatlon.

Discharge coolant from the intercooler mixes with the engine coolantdischarge, and the total coolant flow is pumped back toward the engine.The pump speed determines the rate at which the total coolant flows.However, there is a constant proportionate coolant flow in both theengine and the intercooler, the coolant into the engine being held at aregulated temperature, and the coolant into the intercooler being at atemperature lower than that into the engine, the temperature differenceincreasing with engine load.

In the drawings as hereinafter described, a preferred embodiment isdepicted; however, various other modifications and alternateconstructions can be made thereto without departing from the true spiritand scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a schematic view ofthe preferred embodiment of the invention.

FIG. 2 shows a schematic view ofa modified embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, theinvention is shown generally at and will be described in terms of usagewith an internal combustion engine 11 having a compressor, 15, forcompressing the combustion air to the engine 11, with the compressed aircharge being cooled by an intercooler 12. A typical system of this typeis that of a diesel engine, wherein a turbocharger is driven by theexhaust gases from the engine, and the resultant power is utilized tocompress the ambient air before it is directed to the cylinders. Sinceit is desirable to cool the compressed air and to reduce the maximumcombustion temperature and the turbine inlet temperature, theintercooler has become a standard element in such diesel engine systems.

The primary heat source which requires cooling is the engine cylinders,and this cooling function is accomplished by passing a coolant, such aswater or the like, to an engine inlet line 13, through the enginecylinder jackets 11, and out an engine discharge line 14. It isdesirable to maintain the temperature of the coolant into the engineinlet line 13 at a substantially constant value and to maintain asubstantial flow of coolant through the engine during all periods ofoperation. Coolant flow to the engine is maintained by a standard pump16, typically one of the centrifugal type, having an inlet line 17 anddischarge line 18. The pump is generally driven by the engine, andtherefore the rate of total coolant flow therethrough is determined bythe operating speed of the engine 11.

Connected to and fluidly communicating with the pump discharge line 18is a valve inlet line 19 for proportioning the total coolant flowbetween lines 13 and 19. The system is hydraulically balanced, as forexample, by design or by fixed orifices, so that the flow rates to theengine inlet line 13 and the valve inlet line 19 are in the desiredratio. The inlet line 19 leads to a temperature controlled three-wayvalve 21 having ports B, C and E. The control valve is of the standardcommercially available type, having an integral sensor to sense thetemperature of the coolant coming to the E port and modulating the flowto the C and B ports to maintain the temperature at E and at the engineinlet at the desired value. It modulates, in response to the temperatureof the coolant in line 19, the proportional flow of coolant to a by-passline 22 and to a heat exchanger inlet 23. That portion of the coolantgoing to the line 23 passes through a heat exchanger 24 where it iscooled by the external cooling medium such as air or water or the like,then flows out the discharge line 25, where it mixes with the coolantfrom the by-pass line 22 to cool it. The combined flow then goes throughthe inlet line 26 to the intercooler 12 where it takes heat from thecompressed combustion air. With the engine operating under load, thetemperature of the coolant in line 26 is substantially below that of thecoolant in line 13, thereby providing a very substantial cooling effectto the compressed air. The temperature difference between the enginecoolant and the intercooler coolant is determined by the engine load. Aswill be seen by the examples presented hereinafter, when operating underfull load conditions this temperature difference will be at a maximumand result in maximum cooling of the combustion air, whereas whenoperating at reduced loads, the temperature difference and the amount ofheat taken from the charge air by the intercooler will accordingly bereduced.

Coolant from the intercooler passes through the outlet line 27 to themain line 28 where it mixes with the coolant discharge from the engineto cool it. The total coolant flow then passes to the pump through inletline 17. It should be noted that another heat source, such as an oilcooler, may be placed in line 28, and in such case the temperature ofthe coolant mixture would be brought to a temperature below that of thecoolant into the engine, such that after leaving the oil cooler it wouldbe of the desired temperature. An expansion tank 29 may be provided toaccommodate variations in coolant and ambient temperatures andpressures. It should be noted that the integral sensor may just as wellbe replaced by a remote sensor installed in the engine inlet line 13,with the temperature control valve 21 being equipped for remote sensing.Alternatively, if it is desirable to control the temperature of theengine coolant discharge, it may be regulated by connecting the remotesensor in the discharge line 14.

It would not be particularly desirable in a diesel engine installationto regulate the temperature of the coolant to the intercooler and allowthe coolant to the engine to float at a higher temperature. However,there may be various other cooling schemes wherein the engine andintercooler of FIG. 1 are replaced by elements having differenttemperature requirements and the coolant to the element requiring thecooler temperatures is preferably regulated and that to the elementrequiring the warmer temperatures can be allowed to float. Theserequirements can be met by the identical placement of the control valveas described above but with the remote sensor placed in either of theinlet or outlet lines, 26 or 27. Also, the remote sensor may be placedin the line 31 to regulate the charge air temperature.

Another valve and sensor arrangement which may be used is that shown inFIG. 2 which will be described hereinafter.

In a typical opereational example of the diesel engine installationshown in FIG. 1, the engine is started and the coolant circulatesthrough the system. It is desirable to maintain the temperature of thecoolant into the engine at a temperature of and that into theintercooler at a lower temperature. Until the coolant temperatureapproaches 175, the thermostatically con trolled valve 21 passes all ofthe coolant from line 19 directly to the intercooler 12, by-passing theheat exchanger and facilitating warm-up of the coolant to the engine.Upon the coolants reaching the desired temperature, the valve 21 thenacts to pass portions of the coolant to the heat exchanger, therebypreventing the temperature from increasing beyond 175. As the load onthe engine is increased, a greater amount of cooling is required tomaintain the desired temperature. Accordingly, more coolant is routedthrough the heat exchanger, thereby resulting in lower temperatures atthe intercooler and greater cooling effect on the compressed air. Sinceoperation of the engine at a higher load condition causes theturbocharger to operate at a higher compressor pressure ratio therebyincreasing the temperature of the compressor discharge air entering theintercooler, this is a highly desirable relationship.

Assume that the system is operating under a full load condition and thetemperature rises at the engine and intercooler are F and F,respectively. Assume also that the total coolant flow is 100 gallons perminute of which 75 gpm flows through the engine and gpm through theintercooler. Assuming further that the coolant is water, the heatrejections for the engine and intercooler are then as follows:

BTU/hr Engine: 4500 gal/hr X 10F X 8.33 lb/gal X (l.0) specific heat ofwater 375,000 lntercooler: 1500 gal/hr X 20F X 8.33 lb/gal X (l)specific heat of water 250,000 Total 625,000

Since the heat rejection must all be taken out of the 25 gpm flowing tothe intercooler, the temperature drop across that portion is then A T625,000/(25 X 60 X 8.33) 50F Thus the temperature of coolant into theintercooler is 175 50 125F, and the temperature out is l45F.

At the engine, the coolant enters at 175 and leaves at 185F. Whencombined with the coolant discharge from the intercooler, the mixturetemperature can be expressed by the following formula:

75(T AT 25(T AT2)/100 T where T coolant temperature into pump AT coolanttemperature change through engine T coolant temperature into intercoolerAT coolant temperature change through intercooler This indicates thatthe temperature of the coolant mixture from the engine and intercooleroutlets equals the temperature of the water into the pump. In theexample given:

If the load on the engine and/or compressor is decreased with thecoolant flow remaining constant, the temperature rises across the engineand/or compressor will decrease resulting in a lower temperature ofcoolant into the pump. This will be sensed by the thermostaticallycontrolled valve which will divert more of the coolant directly to theintercooler by-passing the heat exchanger and raising the temperature ofthe coolant to the intercooler to restore the temperature of the mergedcoolant to the desired value.

For example, if the load on the engine and compressor were each reducedso that the heat rejection was only 20 percent of the original value,then the total heat rejection would be 0.2(625,000) 125,000 BTU/hr Thetemperature drop of the coolant flowing to the in tercooler isAT=125,000/(25 X 60 X 8.33) 10F The temperature rise across the engineis AT, 0.2(10) 2F. The temperature rise across the intercooler is AT0.2(20) 4F. The following coolant temperatures then exist:

Engine temperature in 175F Engine temperature out 177F lntercoolertemperature in F lntercooler temperature out l6 9F and the coolanttemperature after merging is again It can therefore be seen that afteran initial warming up period the temperature of the coolant to the pumpand engine remains constant. Also, the temperature of the coolant to theintercooler is lower than that constant temperature by an amountdetermined by the amount of combined heat rejection of the engine andcompressor. Greater loads cause greater differences in the respectivecoolant temperatures. As a no-load condition is approached thetemperatures to the engine and intercooler become equal at F.

This indirect relationship between the engine load or magnitude of theheat source and the temperature of the coolant to the intercooler,facilitates combustion in cold weather by warming the intake air whenthe engine is idling or lightly loaded Typically an intercooler or a"turbocharged engine operating at full load with cooling water in at170F and air in from the compressor at 370F will cool the air to theengine to about F.

On a cold day with the engine idling the same intercooler will bring theair temperature to within l0-l5 ofthe temperature of the water enteringthe'intercooler orabout l55F. Assuming the ambient air temperature is 0Fand the engine has volumetric compression ratio of 12, the temperatureat the end of the compression stroke will be about ll20F versus about800F if the air was not heated by the intercooler. The highertemperature facilitates compression ignition and combustion of the fuelduring periods in which the engine is operating in an idle condition. Incertain applications, as for example in railway locomotive engines, itis common practice to idle the engine during approximately 40 percent ofthe operating time. In cold weather the warming effect of theintercooler on the combustion air charge is important.

Generally the same locomotive is operating under full power during muchof the remaining 60 percent of use time. As mentioned hereinbefore,during these periods critical operating temperatures are reduced byhaving a maximum manifold air cooling capacity. This is automaticallyachieved by decreasing the intercooler coolant temperature as the loadincreases.

Tests of internal combustion engines have shown that reduced inlet airtemperatures bring about a major reduction in exhaust emissions ofnitrides of oxygen (NO For example, at full power they can be reduced toas low as 20 percent of those produced when operating with normal inletair temperatures.

Other advantages offered by the provision of lower air temperatureinclude reductions in engine combustion temperature, turbine operatingtemperatures and exhaust temperature for the same power output, therebyimproving parts life and reducing the requirements for temperaturederating. In many engines the lower temperatures will permit increasedpower output.

Another advantage is the fact that all of the cooling is done on afraction of the flow thereby permitting smaller-piping and flexibilityin the design of the external heat transfer system. Further, the presentsystem provides full coolant flow to the machines at all times,

thereby preventing hot spots, unlike systems which attain temperatureregulation by restricting flow.

Other applications of the present system include but are not limited toengine driven compressors where improved compression efficiency andreduced fuel consumption can be achieved by supplying colder water forcompressor intercooling, and liquid cooled gas turbines where coldertemperatures are desired for compressor intercooling than for turbinecooling.

Referring now to FIG. 2, the apparatus is substantially the same as thatshown in FIG. 1 except that the by-pass line and temperature controlvalve are removed. This arrangement shows the basic concept contemplatedby the invention, i.e., to provide colder coolant to one of two cooledelements by removing the entire heat load from that portion of totalcoolant flowing to the colder element. This may be accomplished withoutthe temperature control valve if there is no necessity to regulate oneof the temperatures as described hereinabove.

If it is desired to regulate a temperature somewhere in the system andit is desired not to modulate the coolant flow in the system atemperature controlled device 32 can be used to control the amount ofcooling by modulating the flow of the external cooling medium throughthe heat exchanger or radiator. If the external cooling medium isliquid, the temperature controlled device is preferably a two waytemperature controlled valve. If a radiator is used and the externalcooling medium is air or gas, then controllable louvres are used tomodulate the flow. Coolant temperatures are sensed by a sensor 33 inmuch the same manner as that described for the apparatus of FIG. 1.Again, the regulated ternperature point may be that in line.19 or it maybe 10- cated at any one of the points described above by the use of aremote sensor.

It should be noted that the temperature controlled device 32 may just aswell modulate the flow of the external cooling medium by being placed ata point downstream of the heat exchanger.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A cooling system comprising:

a. a first heat source to be cooled by the flow therethrough of acoolant at a first temperature;

b. a second heat source to be cooled by the flow therethrough of acoolant at a second temperature lower than said first temperature;

c. means for combining the total discharge flows from said first andsecond heat sources to form a coolant mixture at a temperature no higherthan that of said first temperature;

d. means for pumping said coolant mixture toward the inlets of saidfirst and second heat sources;

e. means for proportioning the total coolant mixture flow between saidfirst and second heat sources; and

f. a heat exchanger means for cooling that proportion of coolant beingdelivered to the inlet of said second heat source.

2. A cooling system as set forth in claim 1 and including a by-pass lineinstalled around said heat exchanger, such that a portion of the coolantflowing to said second heat source does not pass through said heatexchanger but instead passes to said second heat source by way of theby-pass line.

3. A cooling system as set forth in claim 2 and including a temperaturecontrolled valve fluidly interconnecting said proportioning means tosaid heat exchanger and said by-pass line, for proportioning the amountof coolant flow to each in response to an existing temperature conditionin the system.

4. A cooling system as set forth in claim 3 and including a sensor forsensing the temperature of said coolant mixture and modulating saidtemperature controlled valve in response thereto to cause thetemperature of said mixture to be maintained at substantially a constantdesired level.

5. A cooling system as set forth in claim 4 wherein said sensor forms anintegral part of said temperature controlled valve.

6. A cooling system as set forth in claim 1 wherein said heat exchangerhas an external cooling medium flowing therethrough and further whereinmeans is provided to modulate the flow of the external cooling mediumthrough said heat exchanger.

7. A cooling system as set forth in claim 6 and further including atemperature sensitive device for operating said modulation means inresponse to an existing temperature condition in the system.

8. A cooling system as set forth in claim 7 and including a sensor forsensing the temperature of said coolant mixture and further wherein saidmodulation means tends to operate so as to maintain the temperature ofsaid coolant mixture at a substantially constant desired level.

1. A cooling system comprising: a. a first heat source to be cooled bythe flow therethrough of a coolant at a first temperature; b. a secondheat source to be cooled by the flow therethrough of a coolant at asecond temperature lower than said first temperature; c. means forcombining the total discharge flows from said first and second heatsources to form a coolant mixture at a temperature no higher than thatof said first temperature; d. means for pumping said coolant mixturetoward the inlets of said first and second heat sources; e. means forproportioning the total coolant mixture flow between said first andsecond heat sources; and f. a heat exchanger means for cooling thatproportion of coolant being delivered to the inlet of said second heatsource.
 2. A cooling system as set forth in claim 1 and including aby-pass line installed around said heat exchanger, such that a portionof the coolant flowing to said second heat source does not pass throughsaid heat exchanger but instead passes to said second heat source by wayof the by-pass line.
 3. A cooling system as set forth in claim 2 andincluding a temperature controlled valve fluidly interconnecting saidproportioning means to said heat exchanger and said by-pass line, forproportioning the amount of coolant flow to each in response to anexisting temperature condition in the system.
 4. A cooling system as setforth in claim 3 and including a sensor for sensing the temperature ofsaid coolant mixture and modulating said temperature controlled valve inresponse thereto to cause the temperature of said mixture to bemaintained at substantially a constant desired level.
 5. A coolingsystem as set forth in claim 4 wherein said sensor forms an integralpart of said temperature controlled valve.
 6. A cooling system as setforth in claim 1 wherein said heat exchanger has an external coolingmedium flowing therethrough and further wherein means is provided tomodulate the flow of the external cooling medium through said heatexchanger.
 7. A cooling system as set forth in claim 6 and furtherincluding a temperature sensitive device for operating said modulationmeans in response to an existing temperature condition in the system. 8.A cooling system as set forth in claim 7 and including a sensor forsensing the temperature of said coolant mixture and further wherein saidmodulation means tends to operate so as to maintain the temperature ofsaid coolant mixture at a substantially constant desired level.